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It is widely accepted that the current total of 19 surface escorts falls far short of what is needed to meet the UK’s strategic aims. With the Type 26 frigate programme now fixed at 8 ships, the only way surface escort numbers are ever going to be increased is to build more of the cheaper Type 31 frigate (General Purpose Frigate – GPFF). The 2015 SDSR committed government to “at least 19” frigates and destroyers but on 4th November 2016, when talking in the context of frigates, the Defence Secretary said “We will have fleet larger than the fleet at the moment”. This is a positive sign and at least suggests intent in government build more than 5 Type 31 frigates.

Could exports and economies of scale put greater numbers within reach?

The recent devaluation of the pound by 20%, with speculation that its value will bottom out at $1.10 (meaning around a 30% devaluation) makes UK based shipbuilding considerably more competitive than even six months ago. The export potential of a Type 31 and even the Type 26, which until recently appeared very limited, may be more realistic in this new financial reality.

The Treasury-led development of a National Shipbuilding Strategy (NSS) begun in January 2016 and is primarily focussed on naval surface ship construction, is due to report before the Chancellor’s Autumn Statement on 23rd November. The NSS has a lot of ground to cover and the RN must hope it can offer more than George Osborne’s feeble 2015 plan to build one new warship every two years.

France has recently announced construction of its new 4,200 tonne FTI frigate at an estimated cost of £690 million per ship, and shipbuilder DTMI estimates there is market potential for at least 40 such frigates. If government wants a thriving warship building sector, investing a little more in making the Type 31 a more powerful flexible design at a better price point than the FTI offering could reap dividends. UK warship exports lag way behind France and Spain and there is much work to be done to get back into this important market. If government is able to commit to more than the bare minimum 5 ships for the RN, this could leverage economies of scale and increase confidence from potential foreign buyers.

25 escorts, a realistic target ?

The RN manpower crisis may have stabilised by the late 2020s but the lower manning requirements of the Type 26 and Type 31 will be very welcome. The Type 23s and 45s fleet combined needs around 3,550 but the overall requirement should fall by about 1,000 to around 2,550 or allow more vessels to be manned. A younger fleet should be able to offer a slightly higher level of availability.

The 2008 defence review suggested that 30 surface escorts were needed to meet the RN’s operational requirement. Commitments and threats have in no way reduced since 2008.

To escort the operational aircraft carrier and maintain the existing global commitments appears to require, at the very least 10 surface escorts deployed at any one time. Assuming that these units can achieve 40% availability, this suggests a surface fleet of 25 frigates and destroyers. This would require buying 11 Type 31s. In the current climate where the Type 26 construction is not set to start before summer 2017 and the Type 31 exists only on paper, this may seem fanciful. There is some hope that attractive industrial and export benefits with UK-wide construction could just tempt the Treasury to properly back the programme. Currently the future frigate budget is set around £8Bn. If the 8 Type 26 cost around £750M each, as it stands the 5 ‘planned’ Type 31 can have a maximum unit cost around £400M. Adding another 5 or 6 ships to what is already in the funding plan might cost something like £200m per year. This would seem a small price to pay when this could help re-balance the capability of the surface fleet and sustain several shipbuilders for a decade or more.

It seems quite likely the Type 31 will be built by a consortium (similar to the Aircraft Carrier Alliance) led by BAE Systems, but with work shared around UK shipyards. The NSS should shed more light on this but such an arrangement helps spread the economic benefits around the UK and beyond the Clyde which will be largely occupied with Type 26 work.

Can the Type 31 project deliver a credible frigate?

As we touched on in a previous article the Type 31 concept is attempting something extremely challenging. Within a constrained budget and relatively tight timeframe, industry must deliver a frigate that will be an effective platform into the 2030s and 2040s. As an example to avoid, work on the Type 26 will begin two decades after the project to replace the type 23 then called the “Future Escort” was announced in 1997. The 10-year design to delivery schedule will require very tight discipline by the customer in not moving the goalposts during the project and the contractor to deliver on time and on cost. This is possible but will be in contrast to the problems of most large UK defence procurement projects in the last 30 years.

The Type 31 will emerge into a world of new and challenging threats to surface ships. Hypersonic missiles, lasers, weaponised unmanned vehicles and super-quiet conventional submarines are all proliferating. In a high-intensity future conflict, even the Type 26 may have its hands full, will the less sophisticated Type 31 cope?

In terms of design, the basic Type 31 model must be a capable patrol and general purpose frigate, suitably equipped to undertake independent deployment, but also capable of stepping up to act as carrier or amphibious escort if needed. The main cost savings over Type 26 must be found in its smaller size, lighter armament, reduced survivability and more basic propulsion.

If the Type 31 is going to perform as a useful escort then it needs more than self-defence weapons. Like the Type 26, it will still need good sensors, command systems and some self-protection. Assuming Sea Ceptor is fitted then it can provide and basic air defence umbrella over a few ships. Growing underwater threats demands the RN have more anti-submarine platforms. The Type 26 will undoubtedly be a fine submarine hunter but the Type 31 must also be a deterrent to submarines if it is to be considered of real use as an escort. One of the big cost-drivers for the Type 26 are the noise-hygiene measures to reduce the self-radiated noise that impairs passive detection of submarines. The Type 31 will inevitably have nosier propulsion. Perhaps operating a few of its own unmanned underwater vehicles (UUVs) as sensor platforms could be an answer to the Type 31’s need for effective anti-submarine capability on the cheap. The Thales CAPTAS-4 compact offers very small footprint towed array sonar that should also be a minimum requirement for the Type 31. Fitting of anti-ship or land-attack weapons will probably have to take a lower priority.

At around £1Bn each the Type 45 and the Type 26 can almost be considered ‘capital ships’, with which few risks can be taken. A cheaper, more ‘expendable’ ship offers important flexibility on operations. During the Falklands war, lacking available minesweepers, it was the cheap Type 21 frigate HMS Alacrity that that was the sacrificial lamb tasked to sail through Falkland Sound to see if there were any mines. (Fortunately there were none and she survived unscathed).

In conclusion

The Type 31 remains controversial, one respected defence commentator has even called it “the pointless class”. The specification is still very fluid, even within the navy apparently “everyone within NCHQ has a different view”. Ultimately the design will have to be evolved fast and an off the shelf solution seems to be the most realistic way forward. The main image above shows the BMT Venator-110, probably the best baseline option of the 3 outline design proposals for the Type 31 in the public domain at the time of writing. We will examine these proposals in a subsequent article.

What is certain is that the importance of decisions on the Type 31 programme should not be underplayed or seen as of secondary importance to the Type 26 programme. A well designed Type 31 frigate has the potential to maximise the potency of the fleet whilst rejuvenating warship building in the UK. But a leap of faith is needed to choose the right design, and then follow through and build in sufficient quantity to ensure economies of scale.

Many thanks to John Dunbar for his considerable contribution to this article.

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UK looks to outline requirement for new General Purpose Frigate

Excerpt

Although some pre-concept work has been undertaken in Naval Command Headquarters (NCHQ) and the Defence Equipment and Support (DE&S) organisation, there has as yet been no formal guidance on where the new GPFF will sit on the cost/capability curve. “At the moment, the solution space extends from an offshore patrol vessel at one end of the spectrum to a Type 26 ‘lite’ at the other, and everything in between,” one industry source said. “Everyone in NCHQ has a different view as to what it should be.” Source janes.com

Positioning Type 31 GPFF

Image – thinkdefence.co.uk

Vital stats include

Length (overall) 117m

Draught 4.3m

Displacement 4,000 tonnes

Maximum beam 18m

Top speed >25 knots

Range >7,000 Nautical Miles at 15 knots

Crew size 85 personnel

Total accommodation provision 106+18 personnel

Side launched RHIBs, with a third large RHIB within a stern ramp facility

Flexible mission bay

Flight deck and hangar

Image – thinkdefence.co.ukImage – thinkdefence.co.uk

Designing for the Gap: The space between the OPV and the Frigate

Abstract

One of the enduring struggles for the warship designer has been the design of the affordable warship; a ship that offers useful military capability at a fixed and ideally lower price than a pure frigate or destroyer type. BMT has been investigating this design space, through the creation of a patrol ship design called the “Venator 110”, using a variety of tools to measure performance rapidly. A capability modelling tool has been developed to rapidly compare how different designs achieve military roles and how modular systems may be used to enhance a platform. Investigations have also focused on exploring methods of achieving pragmatic enhancements to survivability. These draw on the company’s experience in developing naval and auxiliary ships which use a mix of naval and commercial equipment and practises to “tailor” survivability. Finally, design solutions that offer maximum flexibility have been incorporated within the design to explore their practicality.

Introduction

One of the enduring struggles for the warship designer has been the design of the affordable warship – a ship that offers useful military capability but at a fixed and ideally much lower price than a true frigate or destroyer type. Historically many navies have adopted this type of vessel, for example the Royal Navy’s Type 14 or Type 21 frigates. However, this type of vessel seems to have become less fashionable since the later part of the last century, with many navies choosing to dispose of these vessels although in favour of smaller numbers of high end warships.

Looking forward, with many navies focused on delivering maritime security rather than posturing, and continued world economic constraints, ship designers and builders are again turning to the affordable patrol vessel as an alternative to the frigate. BMT has been investigating this design space, through the creation of a patrol ship / patrol frigate design called the “Venator 110”. As part of this project paper, BMT has developed a capability modelling process to compare how different designs achieve a defined set of military roles and how modular systems may be used to enhance a platform.

Within this paper, this work will be summarised, including a description of the capability assessment tool, methods of achieving pragmatic enhancements to survivability and the impacts of designing warships for flexibility and modular systems.

The Affordability versus Capability Argument

Th e key to affordable design is to understand what the true requirements are, in what environment they are to be conducted, and to prevent requirements creep occurring through more capability being added than strictly necessary. Th e designer needs to keep a close eye on the design being spiralled upwards in the enthusiasm to procure the best possible solution; but he must also be open to the opportunity to achieve extra value where cost in not significantly affected.

It is also true that the “design space” is not uniform and designs do not necessarily grow in proportion to requirements. Rather, it consists of cliff edges and plateaus where the designer can fi nd themselves “on the wrong side” of a step change or where additional capability can be added for modest cost because of the solution adopted. Th is non-linear characteristic of the ship design process is explored further in Reference [1]. Such a process may not be considered appropriate in all situations and as Reference [1] suggests there is no single process able to capture all ship designs.

Th is implies that requirements definition and design development are parallel activities, each being traded towards the goal of an affordable solution. For a warship, there are a range of expectations of capability and often a difficulty to pin down the exact capability need and therein conduct a robust trade; for example if a ship is to be flexible, to what ends? Th e wide range of interpretations is illustrated at Reference [2]. Hence, for the Venator 110 concept the team set out to consider the following:

What, in a defined framework, is the vessel expected to do?

• What coherent steps in military fi t should be considered?• What level of survivability is consistent with the above?• What is the range of flexibility expected and how can this be achieved in a design which is still affordable and buildable?

For small navy combatants, the typical vessel types are expressed as frigates, corvettes or OPV’s. Th e former is typically an ocean going complex combatant and the latter a simple off -shore vessel. Th e Author would contend that a corvette represents a complex but short endurance vessel, whilst a patrol ship would off er longer endurance but be a simpler platform 1. Fig. 2 illustrates this visually. However, these terms do not represent clear boundaries, although when applying in the context of military tasking and threats they are also not necessarily a continuum; there may be gaps where no useful capability exists. Th e variation of cost will in general occur in a diagonal across the diagram as shown; from bottom left to top right represents increasing cost (or fewer platforms for a budget) whilst top left to bottom right represents a line of common cost (or class size) but represents a diff erent sort of delivered capability (trading size / flexibility for warfighting effect / survivability).

For the purposes of the capability model described in this paper, the problem has been addressed by adopting and then tailoring the latest UK Maritime Doctrine, Reference [3], which clearly and concisely identifies a range of Military Tasks. Th e approach taken in the development of the Venator 110 Patrol Ship was to set the requirements against the Maritime Security Roles, whilst being able to fl ex to achieve the International Engagement Role (not requiring concurrent operations and allowing for mission specific fits) and to deliver the maximum Warfighting Role possible from the platform without increasing size, complexity and platform cost (Fig. 3). With this level of understanding, it was also possible to set survivability objectives, including identifying and recording likely threats.

Using Capability Modelling as a Design Tool

A key enabler to trading cost and capability is the ability to “measure” the capability delivered by a design. It is important that such measurements can be traced to the original capability requirements; in this respect the model needs to reflect not only the performance of an individual weapon or sensor system but how each contributes to the roles the ship will perform. The model also needs to be rapid and straight forward to interpret, as complex models involving scenario modelling often take too long to produce results for the design to test the “what if?” questions throughout the design’s concept development.

In the design development of BMT’s Venator 110, a parallel research task was conducted to create and explore the use of a capability modelling tool. The objective of this tool, undergoing continuous development by BMT, is to provide a method which allows the rapid comparison of the capability delivered by design alternatives. The key aspect here is to undertake the comparison in terms of delivered capability rather than performance or systems selected. The tool used is based on a relational database, which provides a means to create a path that traces from the systems provided within the design to the overall capability delivered. Key to this is the recognition that this is a many to many relationship; capability is delivered by combinations of systems (even multi-layered in some cases) whilst a system may contribute to a range of capabilities.

Hence, a capability assessment tool has been developed that allows the mapping of platform capability against a variety of comparators, including Doctrine and Key User Requirements. The objective is to provide a comprehensive and easily understood picture of how a platform’s physical design combined with technical system selection is able to meet key national operational requirements, or otherwise. This methodology allows comparison of the overall capability against the chosen requirements to enable platform comparison. The comparison process can be used in a variety of ways to assess system choices, the implications of specific design changes, or the ability of a platform with chosen capability to meet national requirements.

The capability assessment tool has been developed to enable a clear mapping to be carried out between the demand and supply functions for maritime platforms and the relationships between these are shown at Fig. 4. This tool can be used to assess and understand the capability decisions associated with maritime platform design. The assessment is tailored to suit the specific requirements of each platform type under consideration. This means that the platform comparisons are conducted on a like for like capability basis.

Fig. 4 shows the basic structure of the capability tool. The demand side starts with Doctrine, moving to subsidiary requirements. These requirements within the capability tool were previously developed from British Maritime Doctrine and have produced a detailed structure, consisting in excess of 1,800 comprehensive capability taxonomy statements that cover the maritime capability domain. These requirements are tempered and changed where necessary to reflect the requirements of the particular nation for which the analysis is performed. These requirements are weighted based on their importance in fulfilling the overarching Doctrine. Metrics are defined against the requirements, which represent measurable performance parameters to be achieved.

The supply side of the tool starts at the platform level, moving through a system or group of equipments to an individual item of equipment or platform characteristic. A number of different types of equipment or characteristics contribute to fulfil the requirement. For example under the Armada de la República de Colombia policy statement, Reference[4], ‘Consolidation of Territorial Control’ the requirement to ‘neutralise land targets; Mobile; Infantry’ is included. The requirement for ‘search, detect and track surface targets’, ’identify surface targets’ and ‘determine intent of surface targets’ are also included (amongst others) to capture all of the contributory factors necessary to fulfil the policy.

The metrics assigned to the demand requirements can then be directly linked to the metrics supplied by the selected equipment. The example shown in Fig. 4 (76mm Medium Calibre Gun System) is but one performance metric between one item of equipment and one requirement. Outside of this example shown, the 76mm capability is measured by a number of metrics beyond a simple range analysis. Prior to the final capability diagrams being generated there are a significant number of such weighted performance metrics considered within the tool, to provide a comprehensive view of capability.

The output for each platform variant is plotted as a solid line on the Radar Plot to allow direct capability comparison on a like for like basis, and a representative version of this plot can be seen at the base of Fig. 4. Each axis should be considered separately; a discrete value when comparing platform types. For example, a platform score cannot be directly compared against a score on a different axis for the same platform, but can be compared with another score on the same axis for a different platform, facilitating a direct comparison between platform options.

Survivability

Many ship designers will recognise survivability as a cost driver and many studies have been conducted to identify “affordable” survivability. A fundamental part of providing cost effective survivability is to understand the threats and to ensure that the design presents a balanced solution, such that the correct measures are included to protect against the threats in the environment associated with the tasks that the ship is designed to conduct.

Survivability is a multi-layered capability that enshrines the operational doctrine, equipment and system specification, material design and the operational procedures adopted. Creating a design solution that successfully achieves the right level of survivability requires consideration of all these aspects in a balanced and coherent way. Having a clear understanding of the requirement for survivability is critical for developing both a robust and cost effective approach. There are two elements to defining the approach to survivability:

• The level of capability to be maintained, which defines the aspects of the ship which require protection;

• The threat level, which determines the level of protection to be provided.

As a simplification, an approach taken for a frigate could be to define the worst case threats likely to be encountered and to define the set of capabilities to be maintained (for example, propulsion and key combat systems). This defines the set of equipments and systems requiring protection, the remaining non-critical systems needing no protection. In the case of an OPV, survivability over and above safety considerations under normal operating conditions is paid little attention as these are not considered warships. Often the design is based on the application of (commercial) classification society rule sets to ensure crew and vessels safety in a nonthreatening environment. Neither approach offers significant cost scaling, rather a binary decision to provide protection or not.

However, as OPV like vessels are increasingly seen as force multipliers to supplement warships in limited threat environments and indeed warships are more cost constrained and capability traded, there is a need to consider a more layered approach to ship vulnerability. In defining the threat and capability to be maintained, there may be a case for a scaled approach in which the capability maintained is graduated against increasing threats. This becomes a risk based consideration.

Prescribing proven (military) equipment and systems to achieve vulnerability protection across many systems reduces the risk of vessel loss but adds cost. As the decision is taken to relax the extent of system capabilities retained post damage, or adopting good practise guidance with more commercial approaches rather than specifying tested and proven military equipment, then risk is increased but cost reduced. Ultimately the correct balance point becomes where affordability is achieved with acceptable risk levels for loss of capability during the perceived range of missions.

As a minimum, the vessel needs to offer safety and protection to the crew for all scenarios. In principle, a starting assumption may be that an OPV-like warship may spend much of its time in a maritime security environment in which there is no or limited military threat. The threat may be characterised as man-portable, low technology weapons of short range (e.g. hand weapons, machine guns or rockets). In this situation, the platform is likely to be operating as an independent unit and therefore minimum loss of capability will be preferable. When the same platform is operating at a higher threat level, it will be in operations beyond maritime security and therefore may be assumed as a supporting unit to other more capable units. As a supporting unit, the level of capability to be maintained could be much reduced, perhaps to float / crew safety and potentially only a limited move capability.

This approach allows both ‘capability to be maintained’, and ‘threat’ to be considered and traded for each system to achieve a cost effective policy against the appropriate combinations, as demonstrated in Table 1. It should be noted this is not the same as the disposable warship concept, which suggests warships are produced cheaply such that more vessels balance the greater risk of loss in high threat environments (as envisaged for example by the “Streetfighter” concept, Reference [5]). Here, the argument is that warfighting is primarily delivered by the vessels designed for the purpose whilst a vessel such as the patrol frigate is a supporting asset and therefore the loss of its capability should not represent a significant risk to force level mission success.

Another useful approach to explore is the adoption of classification society rules that offer appropriate levels of vulnerability protection. Although not intended to achieve warship survivability objectives, the use of classification society rules offer a degree of certainty (as they are articulated rules that will not change during design and construction). It would allow use of some commercial practises and equipment suppliers, and many shipyards are familiar with their application and approval against class rules. The wider application of classification society rules and the advantages are discussed in Reference [6].

Whilst adoption of class rules may not mitigate all potential risks, combining classification society rules with project specific guidance to tailor the class notations can result in acceptable performance whilst retaining many “commercial” practises, effectively as “owner’s requirements” would for commercial vessels. This guidance may take the form of prohibiting specific materials in the design of systems or specification of equipments, such as those of a brittle nature (e.g. cast iron) or which are likely to result in dangerous fragments (e.g. glass).

The design of the structure may adopt commercial practises and structural profile sections2.Enhanced performance may be achieved under weapon damage through careful attention to structural details, avoiding those known to have poor resilience to the effect of weapon damage. Again this can be achieved through project specific structural policies and guidance (i.e. avoiding stress concentrations, sharp corners, the use of gussets to spread loads).

Many classification societies have redundant power and propulsion notations (such as the LR PMSR or DNV RPS notations). Adoption of a redundant power and propulsion notation for a patrol ship would ensure that the potential failure leading to loss of the move function (and hence loss of mission) could be reduced to a negligible level. As some of the notations also specify separation of power and propulsion into independent machinery rooms, some degree of protection is afforded to loss of a machinery room due to flood or fire as a result of either accidental or weapon damage.

An example of how this philosophy is applied is the arrangement of the power and propulsion solution. The following approaches could be applied to a ship to offer increasing levels of protection from attack:

• Single engine room and generator room but redundant equipment to class society notation, offering redundancy to equipment failure but no redundancy for compartment loss;

• Separate engine rooms with power and propulsion arranged in each to class society notation, offering redundancy if one compartment suffers flood or fire but with no redundancy if the adjoining bulkhead is breached, e.g. by fragments;

• Separated engine rooms with a protected bulkhead between as an owners enhancement to a class society notation, offering redundancy if one compartment suffers flood or fire and with limited capability to maintain redundancy against fragments and small arms;

• Separated engine rooms with at least one compartment separation as typically adopted for a frigate, offering redundancy against flood, fire and weapons damage to a level consistent with the separation achieved.

The separation of engines rooms offers survivability improvements as illustrated in Reference [7].

However, such arrangements have a significant impact on the design and become a size driver as the engine rooms are forced further towards the ends of the hull and the uptake arrangements require separate funnels. It is therefore important to understand if the improvement in survivability is actually justified by the capability need.

For the Venator 110, given the survivability intent described in Table 1, providing redundancy for power and propulsion as a result of fire or flood in one engine room would offer significant operational advantage, as it would provide for a graceful loss of capability in the event of an accident. Some degree of protection for the separating bulkhead would also mitigate fragment or small arms causing loss of adjacent engines rooms. However, the design impact of separating the engine rooms by another space would outweigh the advantage as it would only enhance vessel survivability against larger threats, which was not a stated design objective. In the smaller Venator 90 design, the separation of the engines is not practical and in this case the solution reverts to the next level, offering redundancy in equipment but not in the arrangement. However, an auxiliary drive may prove attractive in offering a limited level of redundancy.

Modularity as an Enabler

The incorporation of “modularity”, or perhaps more correctly “flexibility” into designs seeks to address a number of objectives as described below (Reference [8] also provides further discussion on modularity):

• Reduce acquisition and through life costs by allowing one ship class to address multiple roles;

• Reduce acquisition and through life costs by allowing one ship to perform the role of several legacy platforms;

• Reduce acquisition costs by simplifying the integration interface between ship and equipment;

• Reduce acquisition costs by simplifying the integration interface between ship and equipment;

However, these perceived advantages must be traded against the cost of incorporating modularity, which includes the cost of developing and purchasing modules; the increased platform size to accommodate modules; and the cost of storing and maintaining modules when not deployed on vessels.

In fact, modularity can be achieved at a variety of levels with differing impacts on platform design and cost, for example from Reference [9]:

• Construction modularity – use of modules to simplify construction interfaces and integration;

• Configuration modularity (e.g. MEKO®-class ships) – use of modularity to allow different configurations to be adopted within one design;

• Mission modularity (e.g. Stanflex series of vessels) – the use of modules to allow one ship to change its capability between missions;

• Battle (network) modularity – the use of modularity to allow one ship to reconfigure elements to adapt capability during a mission.

Table 2 attempts to show the relationship between these objectives and the approach taken to modularity. A further variation in the theme of modularity that is emerging in more recent designs is how modularity is incorporated into the design. Two approaches have been adopted:

• Flexible space able to accommodate a range of different “modules”, equipment and other items (for example, as applied to the USN LCS, UK Type 26 and Danish Absalom Class);

• Specific module spaces allocated around the ship for installing different “types” of module (for example the Danish Stanflex).

The former approach is being increasingly adopted in modern designs as it would appear to offer the most flexible Mission Modularity solution. A large “garage” area, often capable of embarking multiple ISO TEU containers gives the ultimate flexibility; if the capability can be accommodated within then the ship may carry it. However, such “garages” have significant design impacts. Some of these are discussed at Reference [10] and they are generally associated with the large volume required (containers are not a space efficient approach to providing capability) and the subsequent impact on ship size and structural configuration. These impacts are significant enough to warrant the designer to consider if this is really the most cost effective means of delivering the required flexibility.

When conducting the development of the Venator 110 concept, the adopted approach was to consider how a number of “modules” could be provided which require different characteristics. Based on the defined roles (as illustrated in Fig. 3) it was concluded that the capabilities could be provided in a modular form, with corresponding characteristics as illustrated in Table 3.

Th is approach results in a vessel with a number of defined flexible areas, each capable of embarking one or two modules, as an alternative to a single large garage area. This requires a compromise in terms of overall flexibility (now limited by the size of each flexible space) but allows the spaces to be more integrated within the design. The final design solution adopted incorporates three flexible spaces, as illustrated in Fig. 5:

1. Forward, open to the topside and suitable for containers or weapon modules;

2. Midships, suitable for containers which could plug into the aft end of the forward superstructure which contains the command spaces;

3. Aft and adjacent to the hangar, to allow for an additional boat, unmanned vehicles or additional stores.

Conclusions

The design of small surface combatants have in recent years led to a range of different vessel configurations, varying not only in size but in capability and flexibility. This has led to more vessels being designed outside of the traditional frigate or OPV design envelopes. Matching the target vessel cost, achieved capability and ability to survive in the intended threat environment will lead to the increased use of capability and survivability modelling to ensure that the platform designs are capable of delivering against the navy’s requirements. This modelling is becoming necessary as the vessel designs fall outside of the prescribed norms and standards for the traditional vessel types and confidence in the designs robustness requires greater testing at early design stages.

In addition to the cost and capability debate, the increased need for flexibility and the perceived use of modularity to achieve cost savings will lead to complex debates over the correct design solution. Modularity is used to express a range of solutions to different objectives and the designer will need to truly understand the objective to ensure the correct selection of a modular solution.

Acknowledgements

The Author wishes to thank his colleagues at BMT Defence Services who have contributed to this work. In particular, James Johnson and Jeremy Atkins for supplying key elements.